extraction of metals - introduction THE EXTRACTION OF METALS - AN INTRODUCTION This page looks at the various factors which influence the choice of method for extracting metals from their ores, including reduction by carbon, reduction by a reactive metal (like sodium or magnesium), and by electrolysis. Details for the extraction of aluminium, copper, iron and titanium are given in separate pages in this section. From ore to metal What are "ores"? An ore is any naturally-occurring source of a metal that you can economically extract the metal from. Aluminium, for example, is the most common metal in the Earth's crust, occurring in all sorts of minerals. However, it isn't economically worthwhile to extract it from most of these minerals. Instead, the usual ore of aluminium is bauxite - which contains from 50 - 70% of aluminium oxide. Note: We always treat bauxite as if it was aluminium oxide for chemistry purposes, although it is actually more complicated than that in reality. Copper is much rarer, but fortunately can be found in high-grade ores (ones containing a high percentage of copper) in particular places. Because copper is a valuable metal, it is also worth extracting it from low-grade ores as well.

Ores are commonly oxides - for example: bauxite chalcopyrite CuFeS2 . . . and a whole lot of other things as well which we won't actually come across as a part of this topic for UK A level purposes. Concentrating the ore This simply means getting rid of as much of the unwanted rocky material as possible before the ore is converted into the metal. In some cases this is done chemically. For example, pure aluminium oxide is obtained from bauxite by a process involving a reaction with sodium hydroxide solution. This is described in detail on the aluminium page in this section. Some copper ores can be converted into copper(II) sulphate solution by leaving the crushed ore in contact with dilute sulphuric acid for a long time. Copper can then be extracted from the copper(II) sulphate solution. But, in many cases, it is possible to separate the metal compound from unwanted rocky material by physical means. A common example of this involves froth flotation. Froth flotation The ore is first crushed and then treated with something which will bind to the particles of the metal compound that you want and make those particles hydrophobic. "Hydrophobic" literally means "water fearing".

In concentrating copper ores, for example, pine oil is often used. The pine oil binds to the copper compounds, but not to the unwanted rocky material. The treated ore is then put in a large bath of water containing a foaming agent (a soap or detergent of some kind), and air is blown through the mixture to make a lot of bubbles. Because they are water-repellent, the coated particles of the metal compound tend to be picked up by the air bubbles, float to the top of the bath, and are allowed to flow out over the sides. The rest of the rocky material stays in the bath. Reducing the metal compound to the metal Why is this reduction? At its simplest, where you are starting from metal oxides, the ore is being reduced because oxygen is being removed. However, if you are starting with a sulphide ore, for example, that's not a lot of help! It is much more helpful to use the definition of reduction in terms of addition of electrons. To a reasonable approximation, you can think of these ores as containing positive metal ions. To convert them to the metal, you need to add electrons - reduction. Note: In some compounds the metal may not literally be present as a positive ion.

Instead, it may be part of a covalent bond - but will always be the least electronegative element present, and so will carry some degree of positive charge. That means that its oxidation state will always be positive. Reducing that oxidation state to zero (in the raw element) will always involve adding electrons. If you aren't sure about oxidation states you could follow this link to find out about them. If you choose to follow this link, use the BACK button on your browser to return to this page later. Choosing a method of reduction There are various economic factors you need to think about in choosing a method of reduction for a particular ore. These are all covered in detail on other pages in this section under the extractions of particular metals. What follows is a quick summary. You need to consider: the cost of the reducing agent; energy costs; the desired purity of the metal. There may be various environmental considerations as well - some of which will have economic costs. Carbon reduction Carbon (as coke or charcoal) is cheap. It not only acts as a reducing agent, but it also acts as the fuel to provide heat for the process.

However, in some cases (for example with aluminium) the temperature needed for carbon reduction is too high to be economic - so a different method has to be used. Carbon may also be left in the metal as an impurity. Sometimes this can be removed afterwards (for example, in the extraction of iron); sometimes it can't (for example in producing titanium), and a different method would have to be used in cases like this. Reduction using a more reactive metal Titanium is produced by reducing titanium(IV) chloride using a more reactive metal such as sodium or magnesium. As you will see if you read the page about titanium extraction, this is the only way of producing high purity metal. The more reactive metal sodium releases electrons easily as it forms its ions: These electrons are used to reduce the titanium(IV) chloride: Note: This is a good example of a reduction in which the metal isn't originally present as an ion. Titanium(IV) chloride is a covalent liquid. The reduction is from titanium in the +4 oxidation state to the metal in the zero oxidation state. The downside of this is expense. You have first to extract (or to buy) the sodium or magnesium.

The more reactive the metal is, the more difficult and expensive the extraction becomes. That means that you are having to use a very expensive reducing agent to extract the titanium. As you will see if you read the page about titanium extraction, there are other problems in its extraction which also add to the cost. Reduction by electrolysis This is a common extraction process for the more reactive metals - for example, for aluminium and metals above it in the electrochemical series. You may also come across it in other cases such as one method of extracting copper and in the purification of copper. During electrolysis, electrons are being added directly to the metal ions at the cathode (the negative electrode). The downside (particularly in the aluminium case) is the cost of the electricity. An advantage is that it can produce very pure metals. Questions to test your understanding If this is the first set of questions you have done, please read the introductory page before you start. You will need to use the BACK BUTTON on your browser to come back here afterwards. How Is Aluminium Extracted From Bauxite Ore? - highettmetal.com.au June 2012 How Is Aluminium Extracted From Bauxite Ore?

Did you know that aluminium as we know it is not found like this naturally? Even though this handy material is found in over 250 different mineral compounds, it has to be extracted from bauxite, an ore that is mined worldwide. The process to extract the aluminium from its ore is a seemingly complex and time consuming one, and it goes as follows: Bauxite Mining The first step in the process is to mine the bauxite from the earth, mostly from underground deposits (the largest ones can be found in Southern Europe and Hungary). The bauxite is blasted loose and washed to remove any excess clay. Bayer Process The second step is known as the Bayer process, which involves a combination of a chemical extraction and a mechanical separation to extract alumina (the base from of aluminium) from the bauxite. In the first step of the process, the alumina is released from the bauxite when it is crushed and dissolved in sodium hydroxide. The resulting solution travels through a number of filters and separators to remove insoluble particles (leaving a liquefied sodium aluminate). In the second step, the alumina is recovered from this solution when it crystallizes in a precipitation tank.

The alumina settles on the bottom, is dried and ground into a find white powder that can be further refined into metallic aluminium. As you can see, the process used to extract aluminium from the bauxite ore it originates in is fairly complex and requires a number of different machines in order to be completed. Whilst the biggest aluminium manufacturing plants are located in Europe, they do exist here in Australia, just not on the same large scale due to our smaller deposits. aluminium (US: aluminum) ALUMINIUM This page starts by looking at the extraction of aluminium from its ore, bauxite, including some economic and environmental issues. It finishes by looking at some uses of aluminium. Extracting aluminium from bauxite Introduction Aluminium is too high in the electrochemical series (reactivity series) to extract it from its ore using carbon reduction. The temperatures needed are too high to be economic. Instead, it is extracted by electrolysis. The ore is first converted into pure aluminium oxide by the Bayer Process, and this is then electrolysed in solution in molten cryolite - another aluminium compound. The aluminium oxide has too high a melting point to electrolyse on its own. Aluminium ore The usual aluminium ore is bauxite.

Bauxite is essentially an impure aluminium oxide. The major impurities include iron oxides, silicon dioxide and titanium dioxide. Note: Bauxite actually contains one of a variety of hydrated aluminium oxides some of which you can write as Al2O3,xH2O. Since this is in itself a simplification, for UK A level purposes we normally just treat it as impure Al2O3. Purifiying the aluminium oxide - the Bayer Process Reaction with sodium hydroxide solution Crushed bauxite is treated with moderately concentrated sodium hydroxide solution. The concentration, temperature and pressure used depend on the source of the bauxite and exactly what form of aluminium oxide it contains. Temperatures are typically from 140°C to 240°C; pressures can be up to about 35 atmospheres. High pressures are necessary to keep the water in the sodium hydroxide solution liquid at temperatures above 100°C. The higher the temperature, the higher the pressure needed. With hot concentrated sodium hydroxide solution, aluminium oxide reacts to give a solution of sodium tetrahydroxoaluminate. Note: You may find all sorts of other formulae given for the product from this reaction.

These range from NaAlO2 (which is a dehydrated form of the one in the equation) to Na3Al(OH)6 (which is a different product altogether). What you actually get will depend on things like the temperature and the concentration of the sodium hydroxide solution. In any case, the truth is almost certainly a lot more complicated than any of these. The version I am using is perfectly acceptable and is consistent with the aluminium chemistry you will find elsewhere on the site. The impurities in the bauxite remain as solids. For example, the other metal oxides present tend not to react with the sodium hydroxide solution and so remain unchanged. Some of the silicon dioxide reacts, but goes on to form a sodium aluminosilicate which precipitates out. All of these solids are separated from the sodium tetrahydroxoaluminate solution by filtration. They form a "red mud" which is just stored in huge lagoons. Precipitation of aluminium hydroxide The sodium tetrahydroxoaluminate solution is cooled, and "seeded" with some previously produced aluminium hydroxide. This provides something for the new aluminium hydroxide to precipitate around.

Note: This all starts to be a bit of a nightmare if you try to get at the truth of what is happening. There are two separate issues here - both glossed over by most sources. If you like your life to be simple, ignore the rest of this note! You may well find that the product is quoted as Al2O3,3H2O. If you add everything up, that is the same as 2Al(OH)3. So which is it? I suspect that it probably isn't exactly either of these. The aluminium hydroxide originally precipitated doesn't have that formula - it's a simplification. And it will rearrange to form some sort of hydrated oxide, but I doubt whether it is as simple as the other formula suggests! The second thing is to wonder why this reaction happens at all. If you have done any aluminium chemistry, you may recognise that what normally happens is exactly the reverse of this reaction. So why is it going the other way this time? I suspect (although I don't know for sure) that it is an effect of lowering the temperature on the position of equilibrium.

If the formation of the NaAl(OH)4 is endothermic, it would be favoured by high temperatures (the conditions under which the NaAl(OH)4 is formed during the first stage of the reaction). If you lowered the temperature (by cooling the reaction mixture after filtration), it would favour the exothermic change - the reverse. If you know this explanation to be wrong, please get in touch with me via the address on the about this site page. Formation of pure aluminium oxide Aluminium oxide (sometimes known as alumina) is made by heating the aluminium hydroxide to a temperature of about 1100 - 1200°C. Conversion of the aluminium oxide into aluminium by electrolysis The aluminium oxide is electrolysed in solution in molten cryolite, Na3AlF6. Cryolite is another aluminium ore, but is rare and expensive, and most is now made chemically. The electrolysis cell The diagram shows a very simplified version of an electrolysis cell. Although the carbon lining of the cell is labelled as the cathode, the effective cathode is mainly the molten aluminium that forms on the bottom of the cell.

Molten aluminium is syphoned out of the cell from time to time, and new aluminium oxide added at the top. The cell operates at a low voltage of about 5 - 6 volts, but at huge currents of 100,000 amps or more. The heating effect of these large currents keeps the cell at a temperature of about 1000°C. The electrode reactions These are very complicated - in fact one source I've looked at says that they aren't fully understood. For chemistry purposes at this level, they are always simplified (to the point of being wrong! - see comment below). This is the simplification: Extraction of aluminium from bauxite ore | Mastering Chemistry Help search Extraction of aluminium from bauxite ore The extraction of aluminium involves two steps that is, purification of bauxite by Baeyer's process and electrolysis of alumina. 1. Purification of bauxite by Baeyer's process In the Baeyer's process, the bauxite ore is heated with concentrated NaOH solution under pressure ( Aluminum is purified by leaching method ). The alumina dissolves as sodium meta aluminate. The other materials present in the ore are left as insoluble part.

This solution is filtered in ore are left as insoluble part. This solution is filtered off. From the solution Al(OH)3 is precipitated by adding freshly prepared Al(OH)3 to the cold dilute solution and agitating. Al2O3 + 2NaOH -------> 2NaAlO2 + H2O The precipitated Al(OH)3 is dried and ignited to get pure alumina. 2Al(OH)3 --------> Al2O3 + 3H2O 2. Electrolysis of alumina The alumina is dissolved in a mixture of molten cryolite and fluorspar which lowers the melting point. It is then electrolysed in a rectangular steel tank with carbon lining, which serves as cathode. Anode is set of thick carbon rods suspended from the top into the fused Al2O3. The temperature is maintained between 1200 and 1310k. Oxygen is evolved at the anode.

Al2O3 -------> 2Al3+ + 3O2- At cathode: 2Al3+ + 6 electron -------> 2Al At cathode: 3O2- --------> 1.5 O2 + 6 electron Aluminium formed at the cathode gets collected at the bottom of the electrolytic cell from where it is removed periodically. The metal obtained by this method is about 99% pure. Further purification is carried out by Hoop's electrolytic method. The electrolytic refining of aluminum is carried out in Hoop's cell. The cell consist of iron tank having a lining of carbon. It has three layers of molten liquids with different densities. Molten impure aluminum in the bottom layer which along with the carbon lining acts as the cathode. The middle layer is a mixture of molten fluorides of sodium, barium and aluminum in the molten fluorides of sodium, barium and aluminum in the molten state. This act as the electrolyte. Top layer consist of molten pure aluminum in which a number of carbon electrodes are suspended. These carbon electrodes act as the cathode.

When electric current is passed, the aluminium ions from the middle layer move to the top layer and are discharged at the cathode as pure aluminium. At the same time, an equivalent amount of aluminum from the bottom layer migrates to the middle layer leaving behind the impurities. The pure aluminum is removed from the tapping hole from time to time. The Electrolysis of Bauxite | S-cool, the revision website S-cool, the revision website The method The bauxite (red-brown solid) - aluminium oxide mixed with impurities - is extracted from the earth. The extracted aluminium oxide is then treated with alkali, to remove the impurities. This results in a white solid called aluminium oxide or alumina. The alumina is then transported to huge tanks. The tanks are lined with graphite, this acts as the cathode. Also blocks of graphite hang in the middle of the tank, and acts as anodes. The alumina is then dissolved in molten cryolite - this lowers the melting point - saves money! Electricity is passed and electrolysis begins. Electrolysis is the decomposition of a compound using electricity. When dissolved, the aluminium ions and oxide ions in the alumina can move.

At the cathode: Here the aluminium ions receive electrons to become atoms again: At the anode: The oxide ions lose electrons to become oxygen molecules, O2: Uses of aluminium: BBC - GCSE Bitesize: Extraction of aluminium Next Extraction of aluminium Aluminium is the most abundant metal on Earth. Despite this, it is expensive, largely because of the amount of electricity used up in the extraction process. Aluminium ore is called bauxite. The bauxite is purified to yield a white powder, aluminium oxide, from which aluminium can be extracted. The extraction is done by electrolysis. But first the aluminium oxide must be made molten so that electricity can pass through it. Aluminium oxide has a very high melting point (over 2,000°C), so it would be expensive to melt it. Instead, it is dissolved in molten cryolite, an aluminium compound with a lower melting point than aluminium oxide. The use of cryolite reduces some of the energy costs involved in extracting aluminium. Diagram showing cell for aluminium extraction The diagram shows an aluminium oxide electrolysis tank. Both the negative electrode (cathode) and positive electrode (anode) are made of graphite, a form of carbon.

Aluminium metal forms at the negative electrode and sinks to the bottom of the tank, where it is tapped off. Oxygen forms at the positive electrodes. This oxygen reacts with the carbon of the positive electrodes, forming carbon dioxide, and they gradually burn away. Consequently, the positive electrodes have to be replaced frequently, which adds to the cost of the process. Now try a Test Bite - Foundation Read on if you are taking the Higher paper. Page: Aluminum >> Extraction - Bauxite Extraction The first step in extracting aluminum is to remove it from the Earth in mining. This is relatively simple given the abundance of the material. However aluminum is never found isolated in the Earth (due to its reactivity) but instead it is found bound to other elements in compounds. This means that aluminum alone in can never be dug up, but compounds of it, often containing oxygen and silicon, are. Bayer process on industrial scale (click image for enlargement) The bauxite then has to be purified using the Bayer process, whose development changed the course of aluminum's history . The process occurs in two main steps. Firstly the aluminum ore is mixed with the sodium hydroxide in which the oxides of aluminum and silicon will dissolve, but other impurities will not.

These impurities can then be removed by filtration. Carbon dioxide gas is then bubbled through the remaining solution, which forms weak carbonic acid neutralising the solution and causing the aluminum oxide to precipitate, but leaving the silicon impurities in solution. After filtration, and boiling to remove water, purified aluminum oxide can be obtained. The Hall Heroult Process (click image for enlargement) Once purified aluminum oxide has been manufactured aluminum can be removed from it by the Hall-Heroult Method. In this the aluminum oxide is mixed with cryolite (made of sodium fluoride and aluminum fluoride) and then heated to about 980 �C to melt the solids. This is much lower than the temperature required to melt pure aluminum oxide so much energy is saved. The molten mixture is then electrolysed with a very large current and the aluminum ions are reduced to form aluminum metal (at the cathode) and oxygen gas is formed at the anode, where it reacts with the carbon the anode is made from to give carbon dioxide gas. As the process is so long and requires so much energy (in electricity) the aluminum metal obtained is quite expensive, but still it is competitively priced in relation to other metals unlike earlier in its history .

Summary: Aluminum is extracted from the ground in compounds, it is the purified to alumina (aluminum oxide) in the bayer process, and the metal is finally obtained after electrolysis in a cryolite solution. The full process needs a lot of energy and is quite expensive. Continue to the Next Section... Alloys → No notes for this page. extraction of aluminium from bauxite - Gold Ore Crusher extraction of aluminium from bauxite 4.6.3 Extraction of aluminium for PhysicalScience_Gr12 Electrolysis can be used to extract aluminum from bauxite. Aluminum metal is a commonly used metal in industry where its properties of being both light. The metal is present in deposits of bauxite which is a mixture of silicas, iron. 99% pure aluminum. Extracting aluminium from bauxite – aluminium (US – aluminum) Extraction and uses of aluminium. Precipitation of aluminium hydroxide. This page starts by looking at the extraction of aluminium from its ore, bauxite, including some economic and environmental issues. It finishes by looking at some uses of aluminium.

All about National Aluminium Company – redOrbit Bauxite and Alumina 8th Edition The shape and dynamics of the global bauxite and alumina industry are changing, according to a new report from Roskill. New Shape for the Bauxite and Alumina Industry. Aluminium – Wikipedia The chief ore of aluminium is bauxite. Compared to most other metals, it is difficult to extract from ore, such as bauxite, due to the high reactivity of aluminium and the high melting point of most of its ores. Aluminium ( / ˌ æ l j uː ˈ m ɪ n i ə m / AL -ew- MIN -ee-əm ) or aluminum (American English. Electrolysis – Aluminium Extraction – YouTube Extraction of aluminium from bauxite using electrolysis. Nonprofits & Activism. 8 likes, 0 dislikes. Show video statistics. I like this. diagrams of how aluminium is extracted by various method – Zenith Crusher Extraction and uses of aluminium. Extraction of aluminium aluminum recycling sodium by. Methods of productions / heat treatments of Extraction of aluminium Aluminium can be extracted from Phase diagrams of aluminium with various alloying. Extraction of aluminium.

Google – Patent US3497317 – METHOD FOR CONTINUOUS EXTRACTION OF BAUXITE IN A TUBULAR REACTOR – Google Patents US4055218 Aug 23, 1974 Oct 25, 1977 Vereinigte Aluminum-Werke Aktiengesellschaft Method and arrangement for changing the temperature of fluids which form incrustations. US4112047 Jun 8, 1977 Sep 5, 1978 Kaiser Aluminum & Chemical Corporation Pretreatment system for goethitic bauxites. Bauxite mining – Murdoch Research Repository Bauxite ore, which is mined for its aluminium oxide content, varies from relatively low grades deposits in the Darling Range of Western Australia which contain 30-40 % aluminium oxide to higher grades elsewhere which contain 40-60 % aluminium oxide (Bardossy and Aleva 1990. crushing and grinding of the ore of aluminium– Rock Crusher Mill Aluminum ore (bauxite) crushing and Grinding design and manufacture SBM provide the whole production line of Aluminum ore (bauxite) crushing and Grinding.

Aluminum Crushers, Aluminum mining, Aluminum grinding plant, Aluminum ore processing. Aluminum ore crusher,bauxite crushing,aluminum ore Grinding. Aluminium metal and aluminium products – Hydro, a global supplier Hydro is a global supplier of aluminium with activities throughout the value chain, from bauxite extraction to the production of rolled and extruded aluminium products and building systems. Visit us at Bau 2013 and experience our product range of aluminium building solutions. Photo illustrating bauxite products. Aluminium - Fact Sheets - Australian Mines Atlas Suggestions for Further Reading Introduction Aluminium (Al) comprises about 8.2% of the Earth's crust. It is the third most abundant element in the crust and the most plentiful metallic element, but is never found on its own in nature. Bauxite is the ore most commonly mined for aluminium in which aluminium occurs as hydroxide minerals. Aluminium is a silvery-white, tough and lightweight metal (specific gravity 2.7). It is a good conductor of heat and electricity, is very resistant to atmospheric corrosion (it never rusts), is nontoxic, inflammable, nonmagnetic and non-sparking, and it is malleable and ductile.

Because of these properties it has become an important metal. Metallic aluminium was first isolated in 1825 by Hans Christian Oersted from aluminium chloride but it was not commercially produced until 1888 with the establishment of the Pittsburgh Reduction Company (known as Alcoa since 1907). Aluminium can be mixed with almost any other metal and these alloys typically combine lightness with strength. As a result, they are used in a great variety of industries. In Australia, aluminium is produced in Tasmania, Queensland, Victoria and New South Wales with the building and construction industries being the most important consumers. Occurrence In 1821, French geologist Pierre Berthier discovered an aluminium-rich material near the village of Les Baux in Provence, France. It was named bauxite after the village. Bauxite occurs as a weathered cover or blanket, known as laterite or duricrust, over a variety of alumina-bearing rocks. It forms when large amounts of rainfall leach away the more mobile elements in the host rock leaving the relatively immobile aluminium with some silicon, iron and titanium. Because of the way it forms, bauxite deposits can be very extensive and are found on almost every continent.

The largest known economic resources occur in Guinea and Australia, followed by Brazil, Vietnam and Jamaica. The main aluminium minerals in bauxite are gibbsite [Al(OH)3, also written as Al2O3.H2O in oxide notation], boehmite [AlO(OH), written as Al2O3.H2O in oxide notation] and diaspore, which is a polymorph of boehmite but is denser and harder. Pure alumina (Al2O3) contains 52.9% aluminium and 47.1% oxygen. Bauxite may be as hard as rock or as soft as mud and may occur as compacted earth (both friable and re-cemented), small balls (pisolites), or hollow, twig-like material (tubules). Its colours may be buff, pink, yellow, red, or white, or any combination of these. Bauxite ore refers to bauxite that contains sufficiently high levels of Al2O3 and suitably low levels of iron oxide (Fe2O3) and silica (SiO2) to be economically mineable.

The amount of reactive silica is particularly important as this form of silica consumes the caustic soda needed to make alumina, thus low reactive silica is desirable. Other potential sources of aluminium include a variety of rocks and minerals such as aluminous shale and slate, aluminium phosphate rock and high-alumina clays. Australian Resources and Deposits In 2014, Australia was the world’s largest producer of bauxite (30%) and the second largest producer of alumina (19%). Bauxite is mined from established open cut operations at Weipa in Queensland, Gove in the Northern Territory and the Darling Range in Western Australia. Additionally, new mines have begun operation in the Cape York region of Queensland and in central Tasmania. Other bauxite deposits occur in northern Western Australia, New South Wales and eastern Queensland but are currently uneconomic to mine. Australia's bauxite resources are assessed each year by Geoscience Australia. The assessment is based on published and unpublished data. These estimates are published each year in Australia’s Identified Mineral Resources . Once mined, the next stage in aluminium production is the chemical Bayer Process where alumina (Al2O3) is extracted from bauxite in a refinery.

Australia has six alumina refineries: QAL and Yarwun are located in Queensland near Gladstone, and Kwinana, Pinjarra, Worsley and Wagerup are all located in Western Australia in the Darling Range. The final stage of aluminium production takes place in a smelter. The electrochemical Hall-Héroult Process uses huge amounts of power to extract aluminium metal from alumina. (Aluminium is sometimes referred to as ‘solid electricity’ owing to the large amount of power used in its production.) Australia has four aluminium smelters: Bell Bay in Tasmania, Boyne Island in Queensland, Portland in Victoria and Tomago in New South Wales. In 2014, Australia produced the largest amount of bauxite in the world followed by China, Brazil, India and Guinea and the second largest amount of alumina after China. China is the world’s largest consumer of aluminium and, despite strong domestic production, imports large amounts of alumina and raw bauxite, accounting for more than 40% of global consumption. Other large aluminium markets are the United States of America, Japan and Europe but these regions possess few economic bauxite deposits and also rely on imports for their aluminium smelters.

In 2014, Australia produced the seventh highest amount of aluminium in the world after China, Russia, Canada, the United Arab Emirates, India and the United States of America. Australian bauxite, alumina and aluminium statistics are published each year by the Office of the Chief Economist. Mining Extraction of aluminium metal takes place in three main stages - mining of bauxite ore, refining the ore to recover alumina and smelting alumina to produce aluminium. Mining Bauxite is mined by surface methods (open-cut mining) in which the topsoil and overburden are removed by bulldozers and scrapers. The topsoil is then stored and later used for revegetating and restoring the area after mining is completed. The underlying bauxite is mined by front-end loaders, power shovels or hydraulic excavators. Some bauxite ores are merely crushed, dried and shipped. Other bauxite is beneficiated after crushing by washing to remove some of the clay, reactive silica and sand waste and then dried in rotary kilns. The ore is then loaded into trucks, railway cars or onto conveyor belts and transported to ships or refineries.

Refining In almost all commercial operations, alumina is extracted from the bauxite by the Bayer refining process. The process, discovered by Karl Josef Bayer in 1888, consists of four stages. Digestion - in which the finely ground bauxite is fed into a steam-heated unit called a digester. Here it is mixed, under pressure, with a hot solution of caustic soda. The aluminium oxide of the bauxite (and the reactive silica) reacts with the caustic soda forming a solution of sodium aluminate or green liquor and a precipitate of sodium aluminium silicate. Clarification - in which the green liquor or alumina-bearing solution is separated from the waste (the undissolved iron oxides and silica which were part of the original bauxite and now make up the sand and red mud waste). This stage involves three steps: firstly, the coarse sand-sized waste is removed and washed to recover caustic soda; secondly, the red mud is separated out; and, thirdly the remaining green liquor is pumped through filters to remove any residual impurities.

The sand and mud are pumped together to residue lakes and the green liquor is pumped to heat exchangers where it is cooled from 1000°C to around 650-790°C. Precipitation - in this stage, the alumina is precipitated from the liquor as crystals of alumina hydrate. To do this, the green liquor solution is mixed in tall precipitator vessels with small amounts of fine crystalline alumina, which stimulates the precipitation of solid alumina hydrate as the solution cools. When completed the solid alumina hydrate is passed on to the next stage and the remaining liquor, which contains caustic soda and some alumina, goes back to the digesters. Calcination - in the final stage, the alumina hydrate is washed to remove any remaining liquor and then dried. Finally, it is heated to about 1000°C to drive off the water of crystallisation, leaving the alumina, which is a dry, pure white, sandy material. A portion of the alumina may be left in the hydrate form or further processed for the chemical industry.

Smelting All commercial production of aluminium is based on the Hall-Héroult smelting process in which the aluminium and oxygen in the alumina are separated by electrolysis. This consists of passing an electric current through a molten solution of alumina and natural or synthetic cryolite (sodium aluminium fluoride). The molten solution is contained in reduction cells or pots which are lined at the bottom with carbon (the cathode) and are connected in an electrical series called a potline. Inserted into the top of each pot are carbon anodes, the bottoms of which are immersed in the molten solution. The passage of an electric current causes the oxygen from the alumina to combine with the carbon of the anode forming carbon dioxide gas. The remaining molten metallic aluminium collects at the cathode on the bottom of the pot. Periodically, it is siphoned off and transferred to large holding furnaces. Impurities are removed, alloying elements added and the molten aluminium is cast into ingots. The smelting process is a continuous one. As the alumina content of the cryolite bath is reduced more is added.

Heat generated by the passage of the electric current maintains the cryolite bath in its molten state so that it will dissolve the alumina. A great amount of energy is consumed during the smelting process; from 14,000 - 16,000 kilowatt hours of electrical energy is needed to produce one tonne of aluminium from about two tonnes of alumina. The availability of cheap electricity is therefore essential for economic production. Aluminium ingots are produced in various shapes and sizes depending on their end use. They may be rolled into plate, sheet, foil, bars or rods. They may be drawn into wire which is stranded into cable for electrical transmission lines. Presses extrude the ingots into hundreds of different useful and decorative forms or fabricating plants may convert them into large structural shapes. A number of factors in the aluminium production cycle relate to the environment and considerable resources are allocated to minimise the impact of mining, refining and smelting on the surrounding environment. Mine rehabilitation is carried out, making every effort to return the area to at least its original condition. Extreme care is taken also with the handling and disposal of red mud from the refineries.

This is usually pumped into dams which are sealed with impervious material to prevent pollution of the surrounding countryside. Strict measures are taken also to minimise fluoride emissions from smelters and dusty or corrosive material from the refineries. Uses The production of alumina consumes more than 90% of the world's production of bauxite. The remainder is used by the abrasive, refractory, and chemical industries. Bauxite is used also in the production of high-alumina cement, as an absorbent or catalyst by the oil industry, in welding rod coatings and fluxes and as a flux in making steel and ferroalloys. Uses of aluminium include the following: - electrical equipment; car, ship, aircraft construction; metallurgical and chemical processes; domestic and industrial construction; packaging (aluminium foil, cans); kitchen utensils (cutlery, pans). The aluminium industry initiated the development of technology for recycling aluminium containing material and for setting up its own drink can collection centres. One of the industry's main incentives has been the reduced amount of energy it takes to produce one tonne of secondary aluminium compared with one tonne of primary aluminium.

This involves a saving of 95% of the energy required to produce molten aluminium from bauxite. Each tonne of recycled aluminium also means a saving of seven tonnes of bauxite. Suggestions for Further Reading Blainey, G.L. 2003 The Rush That Never Ended: A History of Australian Mining, 5th edition, Melbourne University Press, Melbourne. Coghill, I. 1971 Australia's Mineral Wealth, Sorrett, Melbourne. Ferenczi, P.A. 2001. Iron ore, manganese and bauxite deposits of the Northern Territory. Northern Territory Geological Survey. Report 13. Hughes, F.E. (Ed) 1990 Geology of the Minerals Deposits of Australia and Papua New Guinea, Volumes 1 and 2. The Australasian Institute of Mining and Metallurgy, Melbourne. Aluminum Production & Bauxite Mining: "Aluminum" 1941 OPM 10min - YouTube Aluminum Production & Bauxite Mining: "Aluminum" 1941 OPM 10min Want to watch this again later? Sign in to add this video to a playlist.

Need to report the video? Sign in to report inappropriate content. Rating is available when the video has been rented. This feature is not available right now. Please try again later. Published on Mar 15, 2012 more at "Shows the making of aluminum from the mining of the ore to its use in airplanes. Bauxite is mined in Dutch Guiana, shipped to the U.S. and processed in an aluminum plant. The ore is changed from rock to liquid and then to metal. Shows the rolling of long sheets of the metals Shows the construction of new aluminum plants, dams and power plants, and rolling mills--all essential for aluminum production. Includes many brief shots of military airplanes." NEW VERSION with improved video & sound: Public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied. The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and equalization (the resulting sound, though not perfect, is far less noisy than the original). see also: Aluminium or aluminum... is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13.

It is not soluble in water under normal circumstances. Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal, in the Earth's crust. It makes up about 8% by weight of the Earth's solid surface... The chief ore of aluminium is bauxite. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates. Despite its prevalence in the environment, aluminium salts are not known to be used by any form of life. In keeping with its pervasiveness, aluminium is well tolerated by plants and animals. Due to their prevalence, potential beneficial (or otherwise) biological roles of aluminium compounds are of continuing interest. Physical Aluminium is a soft, durable, lightweight, ductile and malleable metal with appearance ranging from silvery to dull gray, depending on the surface roughness. Aluminium is nonmagnetic and does not easily ignite.

A fresh film of aluminium film serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) of medium and far infrared radiation. The yield strength of pure aluminium is 7--11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has about one-third the density and stiffness of steel. It is easily machined, cast, drawn and extruded. Corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is also often greatly reduced when many aqueous salts are present, particularly in the presence of dissimilar metals. Aluminium atoms are arranged in a face-centered cubic (fcc) structure... Aluminium is one of the few metals that retain full silvery reflectance in finely powdered form, making it an important component of silver-colored paints... Aluminium forms strong chemical bonds with oxygen.

Compared to most other metals, it is difficult to extract from ore, such as bauxite, due to the energy required to reduce aluminium oxide (Al2O3). For example, direct reduction with carbon, as is used to produce iron, is not chemically possible because aluminium is a stronger reducing agent than carbon. Indirect carbothermic reduction can be carried out using carbon and Al2O3, which forms an intermediate Al4C3 and this can further yield aluminium metal at a temperature of 1900--2000 °C. This process is still under development; it requires less energy and yields less CO2 than the Hall-Héroult process, the major industrial process for aluminium extraction. Because of the high melting point of aluminium oxide (about 2,000 °C (3,600 °F)) the pure metal is extracted by electrolysis. In this process, aluminium oxide is dissolved in molten cryolite with calcium fluoride and then reduced to aluminium at a temperature between 950 and 980 °C (1,740 to 1,800 °F).

Cryolite is a chemical compound of aluminium and sodium fluorides: (Na3AlF6). Although cryolite is found as a mineral in Greenland, its synthetic form is used in the industry. The aluminium oxide is obtained by refining bauxite in the Bayer process. The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with potassium.... Category

Question: Which metal is extracted from the ore bauxite?
Answer: Aluminium